Nihal İKİZOĞLU 1. TYPE of CHEMICAL REACTIONS. Balance the following chemical equations. 1. Fe + H 2 SO 4 Fe 2 (SO 4 ) 3 + H 2

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1 TYPE of CHEMICAL REACTIONS Balance the following chemical equations. 1. Fe + H 2 SO 4 Fe 2 (SO 4 ) 3 + H 2 2. C 2 H 6 + O 2 H 2 O + CO 2 3. KOH + H 3 PO 4 K 3 PO 4 + H 2 O 4. SnO 2 + H 2 Sn + H 2 O 5. NH 3 + O 2 NO + H 2 O 6. KNO 3 + H 2CO 3 K 2CO 3 + HNO 3 7. B 2 Br 6 + HNO 3 B(NO 3 ) 3 + HBr 8. BF 3 + Li 2 SO 3 B 2 (SO 3 ) 3 + LiF 9. (NH 4 ) 3 PO 4 + Pb(NO 3 ) 4 Pb 3 (PO 4 ) 4 + NH 4 NO SeCl 6 + O 2 SeO 2 + Cl 2 SYNTHESIS (COMBINATION) REACTIONS Two or more elements or compounds may combine to form a more complex compound. Basic form: A + X AX Examples: Metal + nonmetal salt 2 Na (s) + Cl 2(g) 2NaCl (s) Nonmetal + oxygen nonmetallic oxide C (s) + O 2(g) CO 2(g) Nonmetallic oxide + water acid CO 2(g) + H 2 O (l) H 2 CO 3(aq) N 2(g) + 3H 2(g) 2NH 3(g) NH 3(g) + H 2 O (l) NH 4 OH (aq) Nihal İKİZOĞLU 1

2 ANALYSIS (DECOMPOSITION) REACTIONS A single compound breaks down into its component parts or simpler compounds. Basic form: AX A + X Examples: Metallic carbonates, when heated, form metallic oxides and CO 2(g). CaCO 3(s) CaO (s) + CO 2(g) Some oxides, when heated, decompose. 2HgO (s) 2Hg (l) + O 2(g) Some decomposition reactions are produced by electricity. 2H 2 O (l) 2H 2(g) + O 2(g) 2NaCl (l) 2Na (s) + Cl 2(g) COMBUSTION REACTIONS Combustion means the reaction with O2 gas. So, combustion reactions are also called oxidation reactions. Basic form: X + O 2 X m O n AX + O 2 A a O b + X m O n Products of combustion reactions are always the oxide compounds of each element in the reactant side. Examples: C (s) + O 2(g) CO 2(g) 2Mg (s) + O 2(g) 2MgO (s) CH 4(g) + 2O 2(g) CO 2(g) + 2H 2 O (g) Combustion of Hydrocarbons: When a hydrocarbon is burned with sufficient oxygen supply, the products are always carbon dioxide (CO 2(g) ) and water vapor (H 2 O (g) ) Complete combustion If the supply of oxygen is low or restricted, then carbon monoxide (CO (g) ) will be produced. Incomplete combustion This is why it is so dangerous to have an automobile engine running inside a closed garage or to use a charcoal grill indoors. C (s) + O 2(g) CO 2(g) C (s) + 1/2O 2(g) CO (g) Complete combustion (the higher oxidation number is attained) Incomplete combustion (the lower oxidation number is attained) Nihal İKİZOĞLU 2

3 Hydrocarbon (C x H y ) + O 2(g) CO 2(g) + H 2 O (g) + heat CH 4(g) + 2O 2(g) CO 2(g) + 2H 2 O (g) + heat C 4 H 10(g) + 13/2 O 2(g) 4CO 2(g) + 5H 2 O (g) + heat After all combustion reactions heat is released. That s why, all combustion reactions are EXOTHERMIC REACTIONS. PRECIPITATION REACTIONS Precipitation reactions occur between ions in aqueous solution. When a pair of ions come together to produce a precipitate, this is called precipitation reaction. Basic form: AX (aq) + BY (aq) AY (aq) + BX (s) ppt Examples: NaCl (aq) + AgNO 3(aq) NaNO 3(aq) + AgCl (s) BaCl 2(aq) + Na 2 SO 4(aq) 2NaCl (aq) + BaSO 4(s) In complete ionic equations the all ions in aqueous solution are written: Na + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq) Na + (aq) + NO 3 - (aq) + AgCl (s) Ba +2 (aq) + 2Cl - (aq) + 2Na + (aq) + SO 4-2 (aq) 2Na + (aq) + 2Cl - (aq) + BaSO 4(s) Net ionic equation is the formation equation of a precipitate by its ions: Ag + (aq) + Cl - (aq) AgCl (s) Ba +2 (aq) + SO 4-2 (aq) BaSO 4(s) The ions that are not involved in the actual chemical change are called spectator ions that appear unchanged on both sides of the total ionic equation. Na + (aq) + Cl - (aq) + Ag + (aq) + NO3 - (aq) Na + (aq) + NO3 - (aq) + AgCl (s) Ba +2 (aq) + 2Cl - (aq) + 2Na + (aq) + SO 4-2 (aq) 2Na + (aq) + 2Cl - (aq) + BaSO 4(s) The solubility rules are used to decide whether a product of an ionic reaction is insoluble in water and will thus form a precipitate. Nihal İKİZOĞLU 3

4 Solubility Rules with Exceptions: Rule Exception NO3 - s and CH3COO - s are generally soluble. - Compounds of the alkali metals (1A) and the NH4 + ion are generally soluble. Cl - s, Br - s and I - s are generally soluble. SO4-2 s are generally soluble. - The halides of Ag 1+, Hg2 2+, and Pb 2+ are insoluble. PbSO4, SrSO4, and BaSO4 are insoluble. CO3-2 s, CrO4-2 s, PO4-3 s and SO3-2 s are Many acid phosphates are soluble. generally insoluble. S -2 s are generally insoluble. Except 1A metals and NH4 + OH - s are generally insoluble. Except 1A metals and NH4 + NO2 -, ClO4 -, ClO3 -, ClO2 -, and ClO - s are generally soluble. The hydroxides of Ba, Sr, and Ca are moderately soluble. Experiment (Both precipitation and chemical calculations) Objective: To observe a precipitation reaction and to observe the effects of temperature on solubility based on the reaction between lead (II) nitrate and potassium iodide, to use the limiting reactant to calculate the percent yield of a reaction Materials: lead (II) nitrate, potassium iodide, 2 beakers (250mL), water, graduated cylinder, Erlenmeyer flask (250mL), hot plate, filter paper, funnel, weighing dish. SAFETY NOTE: Safety goggles and aprons must be worn. Procedure: 1. Mass 0.35 g of lead (II) nitrate and 0.3 g of potassium iodide into separate 250 ml beakers. Record mass. 2. Add 50 ml of water to the beaker with potassium iodide and stir. Potassium iodide is very soluble and should dissolve quickly. Observe. 3. Add 50 ml of water to the beaker with lead (II) nitrate and stir. You may need to add a few drops of acetic acid (CH 3 COOH) to acidify the solution and dissolve all of the solid. Make sure it is completely dissolved before continuing. Observe. 4. Slowly mix the two solutions in a 250 ml Erlenmeyer flask. Observe the reaction. 5. Place the flask on a hot plate and turn the heat all the way up. Heat until all solid is dissolved (approx. 15 minutes) 6. Carefully remove the flask from the hot plate and allow it to cool to room temperature. Observe. It can take up to 20 minutes to see any changes occur and placing the flask on a piece of blank paper can help. Allow the solution to cool for at least 35 minutes. Nihal İKİZOĞLU 4

5 7. Set up the filtration apparatus. Mass and label a piece of dry filter paper. 8. After the solution has cooled, carefully filter the mixture to collect the solid. 9. Place the solid and filter paper on a weighing dish and allow it to dry overnight. Observe and mass the next day. Data Collection: Mass of Pb(NO 3 ) 2 Mass of KI Initial observations of Pb(NO 3 ) 2 and KI Mass of filter paper Mass of filter paper and product (PbI 2 ) Mass of product (PbI 2 ) ACTUAL YIELD Limiting Reactant Theoretical Yield of PbI 2 Percent Yield Observations: 1. What happened on the reaction of Pb(NO 3 ) 2 and KI? 2. What happened during heating? 3. What happened during cooling? 4. What did you see on product (PbI 2 ) next day? Analysis and Evaluation: 1. What type of reaction is occurring between lead (II) nitrate and potassium iodide? Nihal İKİZOĞLU 5

6 2. Write a balanced chemical equation for this reaction. 3. Write the complete ionic equation for this reaction. 4. Write the balanced net ionic equation for this reaction. 5. What is the name of the precipitate formed by this reaction? Exercise: Write chemical, complete ionic, and net ionic equations for the following reactions that may produce precipitates. Use NR to indicate that no reaction occurs. 1. Aqueous solutions of potassium iodide and silver nitrate are mixed. 2. Aqueous solutions of ammonium phosphate and sodium sulfate are mixed. 3. Aqueous solutions of aluminum chloride and sodium hydroxide are mixed. 4. Aqueous solutions of lithium sulfate and calcium nitrate are mixed. 5. Aqueous solutions of iron (II) sulfate and barium hydroxide are mixed. 6. (NH 4 ) 2 SO 4(aq) + BaCl 2(aq) 7. Na 2 S (aq) + NiSO 4(aq) Nihal İKİZOĞLU 6

7 8. Al(NO 3 ) 3(aq) + Na 3 PO 4(aq) 9. (NH 4 ) 2 CO 3(aq) + MgSO 4(aq) 10. Ca(OH) 2(aq) + Na 2 SO 4(aq) ACID-BASE (NEUTRALIZATION) REACTIONS Acid is a substance that produces hydrogen (H + ) ions when dissolved in water. HCl (aq) H + (aq) + Cl - (aq) Base is a substance that produces hydroxide (OH - ) ions when dissolved in water. NaOH (aq) Na + (aq) + OH - (aq) When acid and bases solutions are mixed, ions are replaced, H + and OH - ions come together to form neutral water and also an ionic compound, salt. HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l) Acid + Base Salt + Water Net ionic equations of neutralization reactions are the formation of H 2 O equation by H + and OH - ions. Experiment Objective: To produce and isolate a salt by neutralizing a base with an acid. Materials: evaporating dish, 1M hydrochloric acid, 1M sodium hydroxide, phenolphthalein solution SAFETY NOTE: Wear your safety goggles. Hydrochloric acid is an irritant at the concentration used in this experiment. Sodium hydroxide is corrosive and can cause severe burns. Do not touch or taste any of the chemicals. Use tongs to handle the evaporating dish. Exercise care when working with an open flame. Tie back hair and loose clothing. Nihal İKİZOĞLU 7

8 Procedure: 1. Select a small beaker that is just large enough to support your evaporating dish (as shown in Figure). Fill the beaker three-fourths full with water and set up the boiling water bath. While the water is heating, proceed to the next step. 2. Pour 2.0 ml of 1M sodium hydroxide solution into a clean evaporating dish. Add only one drop of phenolphthalein indicator solution to the sodium hydroxide. 3. Add, drop by drop, 1M hydrochloric acid to the evaporating dish, using a dropper. Stir constantly while adding the acid. Continue adding acid until the color of the solution just disappears within one drop. Then add one more drop. 4. Place the evaporating dish over the boiling water bath, as shown in Figure1. Evaporate the solution to dryness. 5. Turn off the gas burner and remove the evaporating dish from the beaker, using tongs. Examine the residue in the evaporating dish. Data Collection: Step Observations Analysis: 1. State the most important safety concern in this lab and the required precaution you took. 2. Write a balanced equation for the neutralization reaction that took place in this experiment. Nihal İKİZOĞLU 8

9 3. Why should you not taste the residue from this reaction, even though the salt produced is commonly used in food? 4. How could you determine whether the phenolphthalein remains in the residue of the reaction (think how you would make phenolphthalein visible)? Reflection: 1. Write balanced neutralization reactions for combining aqueous solutions of the following acid-base combinations: sulfuric acid and potassium hydroxide carbonic acid and barium hydroxide hydrobromic acid and ammonia 2. (Honors) State whether the salts produced in question 1 are acidic, basic, or neutral. Exercise: Write the complete equations for the neutralization reactions that take place when the following water solutions are mixed. a) HNO 3(aq) + Mg(OH) 2(aq) b) H 2 SO 4(aq) + KOH (aq) Write net ionic equation of neutralization reactions: Nihal İKİZOĞLU 9

10 Both precipitation and neutralization reactions are occurred by displacement of ions. So, these reactions are also called double displacement reactions. QUESTIONS: A. Balance the following equations and state what reaction type is taking place: 1. C 5 H 12 + O 2 CO 2 + H 2 O + heat 2. K 3 PO 4 + BaCl 2 Ba 3 (PO 4 ) 2 + KCl 3. Al(OH) 3 + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2 O 4. HCl + K 2 CO 3 CO 2 + H 2 O + KCl 5. AgNO 3 + Na 2 CO 3 Ag 2 CO 3 + NaNO 3 6. Al 2 O 3 + heat Al + O 2 7. P 4 + O 2 P 2 O 3 8. Cu(OH) 2 H 2O + CuO Nihal İKİZOĞLU 10

11 B. For the first few reactions, the type of reaction is listed, you should predict the products, then balance. Further questions just have the reactants listed and you should decide on the type of reaction, as well as the correct products. 1. Combustion: C 6 H 12 + O 2 2. Combustion: C 4 H 6 + O 2 3. Combustion: C 6 H 10 O 3 + O 2 4. Synthesis: Mg + I 2 5. Double displacement: CuCl 2 + H 2 S 6. Double displacement: NaOH + HClO 4 7. Decomposition: ZnCO 3 + heat 8. Single replacement: HCl + Zn 9. Na + MgCl CaCl 2 + K 2 CO K + Cl BaCl 2 + K 3 PO H 2 SO 4 + KOH 14. Al 2 (CO 3 ) 3 + heat 15. Al + O Pb(NO 3 ) 2 + KOH 17. H 2 SO 4 + BaCl Ca + AgCl 19. H 3 PO 4 + FeBr Li + N HCl + Mg(OH) Mg(OH) 2 + heat 23. Fe(OH) 3 + heat Nihal İKİZOĞLU 11

12 C. Record data in the following table. If a precipitate forms, indicate this with ppt. If not, indicate with no ppt. (Make your decision by using solubility rules on pg4) Nihal İKİZOĞLU 12

13 D. Write out the complete chemical formula, the complete ionic formula, and the net ionic formula for the following precipitation reactions. Nihal İKİZOĞLU 13

14 E. Balance the following equations and indicate the type of reaction taking place: Nihal İKİZOĞLU 14